Pull up on the exposed clear plastic tab to peel the battery off the adhesive securing it to the iPhone.

If there's any alcohol solution remaining in the phone, carefully wipe it off or allow it to air dry before installing your new battery.

Remove the battery.

Before reassembly, clean metal-to-metal contact points with a de-greaser such as windex. The oils from your fingers have the potential to cause wireless interference issues.

Perform a hard reset after reassembly. This can prevent several issues and simplify troubleshooting.